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| About the IWMI’s Global Irrigated Area Map (GIAM) Web portal |
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| Welcome to International Water Management Institute’s (IWMI’s) Global Irrigated Area Map (GIAM’s) web portal- a storehouse of products and data related to irrigated areas of the World.
We strongly recommend that you read this introductory note before browsing and downloading products and data.
First and foremost, we recommend you read the Research Report entitled: “An Irrigated Area Map of the World (1999) derived from Remote Sensing”. Also read the working paper entitled: “Methodology for Mapping the Irrigated Areas of the World”. Both these reports are available under the “document” folder of the web portal as IWMI research report and working paper. The GIAM was produced using AVHRR 10-km monthly data for 1997-1999, SPOT 1-km data for each month during 1998, and numerous other datasets including the ground truth data (see the datasets section of the documentation).
There are 4 key product-lines. These are:
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You can click on appropriate places in the front-page that will lead you to the above product line.
When you, for example, click on GIAM you will be lead to an “anchor-page” for GIAM. This page has drop-down menus that will lead you to the product lines: |
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• Maps
• Images
• Class characteristics
• Area calculations
• Snap-shots&
photos
• Animations
• Accuracies |
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| When you drop-down “maps” (e.g., jpeg, tiff) or “images” (e.g., ERDAS .img or ERMapper.ers) you will see “aggregated” and “disaggregated” product line. Most of you may want to use only the aggregated products. These are our definitive final products with clear final class identification and labeling. The disaggregated products provide greater details and have large number of classes. For example, the GIAM aggregated map is a 28 class irrigated area map of the world. The disaggregated is refined into 280 classes- 10 sub-classes for each of the 28 classes. So, we have labeled them as “sub-class 1 of class 1, sub-class 2 of class 1, and so on”. But the sub-classes have not been identified and labeled by us and it is for the user to identify them. Images are similar to maps, except that these are original image files such as ERDAS Imagine and can be used to make your own maps.
The area calculations provide area tables and the methods used to determine areas. Please read the documentation for further information.
Class characteristics provide the mean spectral profile of classes for each of the 12-months and help determine type of irrigation (e.g., single crop, double crop), beginning-peak-end of cropping season, and help compare and contrast classes quantitatively.
Snap-shots and photos, illustrate each irrigated area class in “zoom-in” view using Geocover 150-m data and digital photographs from around the world from precise locations.
Animations, perform monthly AVHRR NDVI simulations of irrigated areas over 20-years and provide a spatial view of the changes that occur month-by-month.
Accuracy assessments were performed through comparison with Google earth data and ground truth data.
The above approach was repeated for the product lines 3 and 4. Even though, the number of products may be less as our emphasis and focus was on GIAM. |
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| It is important to note that the aggregated product line for GMRCA is based on the 9 aggregated classes and 66 disaggregated classes. The product line for GMLULC is based on the 17 aggregated classes and 73 disaggregated classes.
The product line 4 is a distinct product line. The analysis of GIAM and other product lines were performed using image segments based on precipitation, temperature, elevation, and forest cover. These segments were, for example, precipitation less than 360 mm per year segment (PLT360-segment), and Elevations greater than 1500 m segment (EGT1500-segment) (please refer to documentation for details). For each segment the irrigated area and other land use/land cover (LULC) classes were identified and labeled. There were large numbers of discreet classes unique to a segment. We put all the classes from world’s different segments (there were 7 segments) into a single global map which we call Global-IWMI-Generic-951-class-map. This map has highly discreet 951 class map. The purpose of this map is for the users from specific parts of the world to download data and create there own, more defined, map of irrigated areas (or for that matter LULC) for their part of the world using their local knowledge. The class names can then be changed to suite the local specificity. Indeed, we welcome users to produce such maps and share them with us. We may use such information in our next version giving due credit to contributors, but we (IWMI) will own the primary ownership. |
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| In addition to above products, the base datasets used of produce GIAM and other product lines are also made available, including ground truth datasets. These can be accessed through drop-down menus in GIAM “anchor-page”.
• Datasets
• Ground-truth data |
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| All data and products can be viewed by anyone. Those who require to download our products will need to register (which will take you no more than 2 minutes).
Please help us “ground-truth” your area of interest by filling “your comments” form that is available on front page and that you can fill directly online.
Take a look at some of the presentations that may help you understand our work better.
Also, look for future updates.
Finally, we welcome your comments and criticisms- please write to the project team (preferably with CC to everyone). |
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